1. Field of the Invention
Embodiments of the present invention, at least as discussed herein, relate to a recording and/or reproducing apparatus with an optical pickup actuator having high thrust, and more particularly, to a recording/reproducing apparatus with an optical pickup actuator having high thrust and alternating current (AC) sensitivity suitable for high capacity recording media, such as blue-ray discs (BDs) or HD-DVDs.
2. Description of the Related Art
An optical pickup actuator in an optical recording/reproducing apparatus records and/or reproduces information to/from an optical recording medium, e.g., mounted on a turntable, that is, the recording and/or reproducing can be achieved with an optical disc in a non-contact way while moving over the optical disc along a radial direction thereof, for example. The optical pickup actuator may includes an objective lens and an actuator, With the objective lens focusing light emitted from a light source to form an optical spot on the optical disc. The actuator may control the objective lens in a tracking direction, a focusing direction, and a tilt direction, for example, so that the optical spot can be formed at a precise location on the optical disc.
FIG. 1 illustrates a conventional optical pickup actuator. As shown in FIG. 1, the conventional optical pickup actuator includes a base 100, a holder 103 fixed onto the base 100, a lens holder 107 for fixing an objective lens 105, a plurality of suspension wires 130, connected between the lens holder 107 and the holder 103, to support the lens holder 107 so that the lens holder 107 can move with respect to the holder 103, and a magnetic driving unit for driving the lens holder 107 in a tracking direction, a focusing direction, and/or a tilt direction. The magnetic driving unit includes a magnet 110 installed on the base 100 and a plurality of coils 120, 122, and 125 installed on the lens holder 107. The lens holder 107 may be driven by an electro-magnetic force generated when current is applied to the coils 120, 122, and/or 125 within a magnetic field produced by the magnet 110. The tracking, focusing, and/or tilting performances of the optical pickup actuator depend upon an arrangement of the magnet 110 and the coils 120, 122, and 125. Hence, the arrangement of the magnet 110 and the coils 120, 122, and 125 of the magnetic driving unit is very important in the design of the optical pickup actuator.
Recently, there has been a trend toward developing and utilizing high-capacity recording media, e.g., optical recording media such as blue-ray discs and HD-DVDs, which are capable of storing information of several tens of giga bytes. However, to realize a high-speed recording/reproducing apparatus capable of fast recording information to and/or reproducing information from such high capacity media, a corresponding optical pickup actuator should have an improved AC sensitivity over conventional designs. It has been found that the AC sensitivity of the optical pickup actuator may be improved by reducing the weight of the actuator, by increasing the thrust of the actuator, or by other methods. However, optical pickup actuators for blue-ray discs or HD-DVDs, for example, have an increased number of components compared to the conventional optical pickup actuators for compatibility with existing CDs or DVDs. So, increasing the AC sensitivity by reducing the weight of the optical pickup actuator may not be fruitful. For example, optical pickup actuators for conventional CDs or DVDs may typically weigh about 400 mg, while optical pickup actuators for BDs or HD-DVDs may weigh about 500 mg, which is about 20-30% greater than the weight of the optical pickup actuator for conventional CDs or DVDs. Consequently, to achieve fast recording/reproduction, optical pickup actuators for BDs or HD-DVDs, for example, must have increased thrust, since the option of reducing the weight may be difficult. The magnetic driving unit for such an actuator must, thus, be designed so as to increase the thrust of an optical pickup actuator for high capacity recording media, such as BDs or HD-DVDs.
However, in many cases, when optical pickup actuators for such high capacity recording media are designed, the corresponding magnetic driving units do not generate sufficient strong thrust, or the thrust may be sufficient, but tilting becomes impossible. Similarly, although tilting may be possible, a natural tilt may occur in the optical pickup actuator, or a linearity of the optical pickup actuator may be degraded.